Recently, Internet technology has been developed such that prior life style and paradigms of thoughts are changed large. Every country in the world competitively makes an effort to increase Internet use through the construction of super-high speed network, development of various multimedia content, magnification of communication markets, etc., to construct an intellectual information-based society.
Such an Internet has been used to exchange various and useful information among Internet users. However, since the Internet has open features in which Internet users are not restricted to access Internet sites, it has an opposite effect in the children can easily access undesirable web sites such as obscene web sites that can be indiscriminately constructed.
In conventional systems, such undesirable web sites are blocked by installing undesirable information blocking software at client PCs, or by installing an undesirable information blocking system on a LAN in case of schools, organizations such as corporations, and so on.
The former is usually performed in homes for restricting access to undesirable web sites associated with pornography, narcotics, etc. by parents. However, if parents' ability for handling the PCs is less than that of their children, they cannot substantially block access to the undesirable web sites in homes such that their children can access the undesirable web sites.
The latter is performed in a LAN formed in schools or organizations. However, the latter has a drawback in that it entails high maintenance costs and time because the servers must be managed by a full time manager.